Electrical heating envelopes

ABSTRACT

An electrical heating envelope which includes a metallic layer interposed between a vessel, the contants of which are to be heated, and the heating elements which supply the thermal energy. The metallic layer will typically be comprised of non-magnetic material and a layer of resilient insulating material may be positioned between the plate and vessel.

United States Patent 1191 Thibault ELECTRICAL HEATING ENVELOPES [76]Inventor: Jacques P. Thibault, 24, av.

Theophile Gautier, 75 Paris 16 eme, France 22 Filed: o.4,1973 21App1.No.:403,433

Related US. Application Data [62] Division of Ser. No. 157,551, June 28,1971, Pat. No.

1111 3,829,655 Aug. 13, 1974 Primary Examiner-Velodymyr Y. Mayewsky [57ABSTRACT [56] References Cited An electrical heating envelope whichincludes a metal- UNITED STATES PATENTS lic layer interposed between avessel, the contants of 1,492,146 4/1924 Thornton, Jr 219/436 which areto be heated, and the heating elements 2,215,042 9/1940 Howard et a1. 1219/529 which supply the thermal energy. The metallic layer 2,282,0785/1942 Morey 219/436 will typically be comprised of non-magneticmaterial 2,482,665 9/1949 Geyer 2l9/529 and a layer of resilientinsulating material may be posi- Bergen et ai X tioned between the plateand vessel 2,643,324 6/1953 Goldstaul 219/529 2,739,220 3/1956 Morey219/535 5 Claims, 2 Drawing Figures tv/ J i a r i /8 l 5 i r 7 I l f I wJ -J I f 4 1 l 5 I I 2 i f I a 1 ELECTRICAL HEATING ENVELOPES This is adivision, of application Ser. No. 157,551, filed June 28, 1971, now US.Pat. No. 3,772,500.

BACKGROUND OF THE INVENTION 1. Field of the Invention 2. Description ofthe Prior Art Methods of and apparatus for electrically heating thecontents of a flask or other container are well known in the art. Thetypical prior art device will comprise a generally cylindrical shapedouter envelope which may, for example, be comprised of aluminum. Theenvelope forms a housing for resistors which function as heatingelements. The resistors are usually insulated by glass or asbestosbraiding and are sewn within asbestos fabric placed between two glassfiber layers. The insulating and supporting medium for the resistors ispositioned in such a manner as to distribute the resistors regularlyabout the entire lower surface of a vessel which may receive thesubstances to be heated.

The prior art heated envelopes of the type briefly discussed above arecharacterized by a number of well known deficiencies. Firstly, the heattransfer efficiency of these devices is not particularly high. Secondly,in cases where the actual container for the material to be heated iscomprised of a material such as glass which fractures easily, the priorart devices provide no protection for the heating elements which maybecome damaged by the contents of the container in the case of acontainer wall failure.

Further deficiencies of prior art heating envelopes include the factthat they typically are not flameproof and therefor pose a safetyhazard. Also, in the interest of regulating the operating temperature,prior art heating envelopes have provided only for the control ofcurrent to the heating elements or resistors. Considering the mass ofthe resistors, this is at best a slow control method which is lacking inprecision.

SUMMARY OF THE INVENTION The present invention overcomes the abovediscussed and other deficiencies and disadvantages of the prior art byproviding a novel and improved technique for electrically heating thecontents of containers and a heating envelope for use in the practice ofsuch technique. In accordance with the present invention, a metallicplate member is interposed between the heating elements and therecipient of the heat. The metallic plate member will preferably becomprised of a nonmagnetic material and a sheet of insulating fabric maybe positioned between the plate and heat recipient.

In accordance with one embodiment of the invention, the metallic platemember is in the form of a block which is sufficiently thick so as toenable the heating element resistors to be embedded therein. The blockmay also be provided with passages through which a coolant may becirculated in the interest of temperature control. Also in the interestof temperature control, the invention may include a thermocouple orequivalent device which senses the temperature of the metallic plateand, through appropriate circuitry, regulates the flow of current to theheating elements and/or the flow of coolant through the passages in themetallic plate member.

BRIEF DESCRIPTION OF THE DRAWING The present invention may be betterunderstood and its numerous objects and advantages will become apparentto those skilled in the art by reference to the accompanying drawingwherein like reference numerals refer to like elements in the severalfigures and in which:

FIG. 1 is a cross-sectional, side elevation view of a first embodimentof the invention; and

FIG. 2 is a cross-sectional, side elevation view of a second embodimentof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to FIG. 1,the housing for the heating appliance of the present invention isindicated at 1. Housing 1, which may be comprised of any suitablematerial, will typically have a cylindrical outer shape and the voidstherein will be filled with a thermal insulating material 2 of glasswool or other equivalent material.

A non-magnetic sheet metal member 3 is shaped so as to provide a seatfor a container, not shown, which will function as the recipient of heatproduced by the present invention. Thus, by way of example, plate 3 maybe contoured so as to receive a glass flask and the plate may beprovided with a tubular neck receiving portion 4 which accepts thetubular necks with which certain flasks are provided.

The heating element for the embodiment of FIG. 1 comprises a pluralityof resistors 5 which are sewn, in a manner well known in the art, intoand enveloped by an asbestos sheet 6. The metallic member 3 is coveredby another asbestos sheet member 7 which prevents contact between theheat recipient and the heated metallic member 3. Asbestos sheet 7 alsocompensates for small differences in shape and size between therecipient container and the contour of member 3.

Electric current for heating purposes is delivered to the resistors 5via a standard connector 8. The delivery of current to the resistors andthe operation of the invention are in accordance with well knowntechnology and will not be described herein.

Referring now to FIG. 2, the second disclosed embodiment of theinvention will be described only insofar as it departs structurally fromthe previously described embodiment. A principal difference between theembodiments of FIGS. 1 and 2 is that the nonmagnetic sheet metal member3 is in the form of a block 11 in the FIG. 2 embodiment. As shown, inthe FIG. 2 embodiment the metallic block 11 will be sufficiently thickso as to enable the resistors 5 to be embedded therein. The metallicblock may be obtained by casting or by metalization; that is, bypulverizing the material on a bed of fabric which is preferably theinsulating fabric, the electrical resistors becoming embedded during thepulverization. The metallic block may also be produced by otherequivalent processes.

Also in accordance with the FIG. 2 embodiment, the member 1 1 may beprovided with a refrigeration circuit defined by tubes or passages 12formed in or enveloped by the material which defines the block 11. Acoolant may be circulated through passages 12 when it is desired torapidly reduce the temperature of member 11 and the contents of the heatrecipient container.

It is to be noted that the asbestos sheet member 7 of the FIG. 2embodiment may be either separate from the member 11 or may be integraltherewith depending upon the method of manufacture employed in thefabrication of the metal block.

As shown inFlG. 2, the connector 8 is liquid-tight and flameproof. Theconnector housing contains a conventional temperature regulator whichissupplied with an input signal from a thermocouple 9; thermocouple 9either being embedded in member 11 or in contact with an inner surfaceof metal member 11. The operation of and circuitry comprisingtemperature regulator 10 are in accordance with the state of the art andwill not be described in detail herein. Itis to be noted, however, thatthe thermocouple and regulator provide for the automatic control of theextent of heating through controlling the delivery of current to theheating elements. In this manner, the temperature of the appliance maybe maintained below the minimum temperature above which a flash may beproduced. A flash could result either through breakage of the heatedrecipient flask or by passage of vapors escaping from the flask intocontact with the block 11.

If deemed desirable, the regulator 10 may also be employed to controlthe flow of coolant through the passages 6.

As will now be obvious to those skilled in the art, the presentinvention provides for better protection of the heating resistors in thecase of breakage of the heat recipient container. Similarly, the use ofa non-magnetic heat transfer member, in the nature of metal members 3and 11, permits agitation to be affected from below by magnetic means.The asbestos sheet 7 prevents direct contact between the heated surfaceof metal mem bers 3 and 11 and the walls of the recipient container.

While preferred embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the present invention. Thus, while theinvention has been described in the environment of a heating envelopefor delivering thermal energy to flasks and other containers, it may beapplied to such devices as heated reactors, heated funnels, heatedmuffs, heated feeding bottles, heated basins, heated fondues and otherdevices. Accordingly, it is to be understood that the present inventionhas been described by way of illustration and not limitation.

What is claimed is: 1. An electrical heating envelope for supporting andheating containers comprising:

a thermally insulating housing; reentrant vessel receiving meansdisposed within said housing and supported thereby, said vesselreceiving means including a first member comprised of a heat conductivemetal which defines a recess shaped to receive a container to be heated;

electrically energized heating means positioned within said housing incontact with a first surface of said first member, said heating meanssubstantially conforming to said first surface, said heating meansincluding a plurality of resistors enclosed in an electricallynonconductive envelope; and

an inner member including a layer of thermal insulating fabric materialinterposed between the second surface of said receiving means firstmember and a container to be heated whereby containers to be heated aredisposed in said recess on said fabric material.

2. The apparatus of claim 1 wherein said vessel receiving means firstmember is comprised of nonmagnetic material.

3. The apparatus of claim 1 wherein said heating means envelopecomprises: thermal insulating fabric.

4. The apparatus of claim 3 wherein said housing and vessel receivingmeans define a void therebetween and wherein said void is filled with athermal insulating material.

5. The apparatus of claim 2 wherein said vessel re ceiving means firstmember is comprised of nonmagnetic material.

1. An electrical heating envelope for supporting and heating containerscomprising: a thermally insulating housing; reentrant vessel receivingmeans disposed within said housing and supported thereby, said vesselreceiving means including a first member comprised of a heat conductivemetal which defines a recess shaped to receive a container to be heated;electrically energized heating means positioned within said housing incontact with a first surface of said first member, said heating meanssubstantially conforming to said first surface, said heating meansincluding a plurality of resistors enclosed in an electricallynonconductive envelope; and an inner member including a layer of thermalinsulating fabric material interposed between the second surface of saidreceiving means first member and a container to be heated wherebycontainers to be heated are disposed in said recess on said fabricmaterial.
 2. The apparatus of claim 1 wherein said vessel receivingmeans first member is comprised of non-magnetic material.
 3. Theapparatus of claim 1 wherein said heating means envelope comprises:thermal insulating fabric.
 4. The apparatus of claim 3 wherein saidhousing and vessel receiVing means define a void therebetween andwherein said void is filled with a thermal insulating material.
 5. Theapparatus of claim 2 wherein said vessel receiving means first member iscomprised of non-magnetic material.